There is conventionally provided an edge replacement type side cutter as one of rotary cutting tools that can perform groove processing. In the edge replacement type side cutter, a plurality of cutting inserts are typically disposed in a staggered configuration on an outer peripheral portion of the side cutter body. In such a side cutter, an overlap amount between a rotation trace of a cutting edge for groove bottom processing in the cutting insert attached to one end surface of the side cutter body and a rotation trace of a cutting edge for groove bottom processing in the cutting insert attached to the other end surface of the side cutter body is set to be a predetermined amount.
Patent Literature 1 discloses a side cutter in which a plurality of cutting inserts are disposed in a staggered configuration. The cutting insert of this side cutter has upper and lower surfaces each of which is formed in a parallelogram shape.
On the other hand, there is a milling cutter that is used as one of the rotary cutting tools. Patent Literature 2 discloses a cutting insert for the milling cutter. The cutting insert has a substantially hexagonal shape in a planar view, and is a negative type cutting insert. The cutting insert is configured such that an edge portion of each of an upper surface and a lower surface thereof is provided with three cutting edge portions each of which is formed along the corner of each surface, and a total of six corners of the upper and lower surfaces can be used for cutting. Lengths of the side portions of the upper and lower surfaces all are substantially equal, and the length of each side portion is approximately a half of the width of the cutting insert. In this cutting insert, two side portions each having an equal length extend in different directions from one corner having a corner inner angle of 90 degrees in a planar view, and a major cutting edge and a minor cutting edge in a single cutting edge portion are formed in each of these side portions.
In addition, Patent Literature 3 discloses a cutting insert that is used in an end mill and has a substantially hexagonal upper surface. The upper surface of the cutting insert has a rotation symmetrical shape around an axis, and has long side portions and short side portions disposed alternately. Cutting edges of this cutting insert are formed only in an edge portion of the upper surface, and the cutting edge comprises a side edge formed in the long side portion and a bottom edge formed in the short side portion. Further, in the cutting insert, for improving discharge of chips, a width of a chip breaker in a direction of crossing the cutting edge is gradually wider and a depth of the chip breaker is gradually deeper from a leading end of the cutting edge to a rear end of the cutting edge.